1. Field of the Invention
The present invention relates to a process for production of a magnet, a magnet obtained thereby and a production apparatus for molded articles for magnets.
2. Related Background Art
Ferrite magnets are widely used in various fields including automobiles, household electrical appliances and industrial equipment because of their excellent properties and relatively low cost.
For production of a ferrite magnet, first a mixture of starting materials in a prescribed mixing ratio is calcined to obtain a calcined ferritized body, and then the calcined body is pulverized to the submicron size to obtain finely pulverized powder composed of ferrite particles. The finely pulverized powder is then subjected to compression molding in a magnetic field to obtain a molded article, and the molded article is sintered. This process yields a ferrite magnet.
Such molding processes are largely classified as dry molding wherein the finely pulverized powder is molded after drying, or wet molding in which the finely pulverized powder is prepared as a slurry before molding, with wet molding being preferred for a greater degree of magnetic orientation.
Processes for production of magnets by wet molding are known, such as described in Japanese Patent Laid-open No. 2006-253526, for example. The magnet production process described in the aforementioned publication employs a molding apparatus comprising a mortar die with a through-hole, a drag that is inserted into the through-hole of the mortar die and a cope which forms a cavity by sealing the through-hole together with the drag, wherein a slurry supply gate for supply of slurry is formed in the inner wall surface surrounding the through-hole of the mortar die. The slurry supplied to the mortar die with a pump is fed into the cavity through the slurry supply gate.
In this magnet production process, the slurry supplied to the mortar die by the pump is fed into the cavity through the slurry supply gate causing the cavity to become filled with the slurry, after which the drag is moved to accomplish compression molding of the slurry while blocking the slurry supply gate, to obtain a molded article.